Flight simulation system



Jan 2, 1951 D. H. EWING FLIGHT SIMULATION SYSTEM Filed April 30, 1948 60ks .Qa u kSukB N M m A w x A M g u 0 mm D w w mm I 8 v Mm Q Q n u NPatented Jan. 2, 1951 FLIGHT SIMULATION SYSTEM Douglas H. Ewing,Westmont, N. 'J., assignor to Radio Corporation of America, acorporation of Delaware Application April 30, 1948, Serial No. 24,155 Y4 Claims. (01. 235-61) This invention relates generally to therepresentation and control of air traffic, and more particularly toimprovements in the art of simulating or depicting the flight of anaircraft.

The principal object of the invention is to provide methods and meansfor converting continuously one type of representation of flight intoanother type of representation. For example, the flight of an aircraftcan be defined in terms of its starting point (or its position at acertain instant) its ground speed, and heading. The same information canbe presented in an entirely different form, such as the direction andradial distance of the craft from a reference point. The latter form ofpresentation is that ordinarily provided by ground-based radarequipment. The former is similar to that obtained on the aircraft bynavigational means.

It is a specific object of the invention to provide systems forconverting one of the above-described forms of presentation to theother.

Another object of the invention is to provide systems of theabove-described type in which the necessary computations are effected byelectrical means, wherein quantities such as speed, distanceyand anglesare ing voltages.

A further object of the present invention is to provide systems of thedescribed type which are simple to design and construct, and rapid andaccurate in operation.

The invention will be described with reference to the accompanyingdrawing, wherein:

Figure l is a diagram illustrating the geometry which relates the twoabove-described forms of presentation, v

Figure 2 is a schematic diagram of a system converting ground speed andheading information to range and azimuth, i. e. distance and dirctioninformation, and

Figure 3 is aschematic diagram of a system involving the same principlesas that of Figure 2 for converting range and azimuth information toground speed and heading information.

Refer to Figure 1. It is assumed that an aircr'ait is at present attheposition represented by thepoint P. The point is a reference point Irepresented by correspondsuch as the location of a ground based radarstation, and the line N.-S is a directional reference line such as thelocal meridian through the point 0.

The position of the craft at the point P is denoted, in' polarcoordinates referred to the point 0, by theilrange or distance R and theazimuth or directionfi. The ground speed of the craft is Hseparatelyexcited'or permanent magnet field 5o designated by the vector ve; thedirection of the vector referred to that of the line NS is the heading,0:.

If the range R0 and azimuth 00 at some partic- 1 ular instant are knownor assumed, and the ground speed Va and heading a are availablecontinuously, the range R and azimuth 0 at any other instant can bedetermined. The system of Figure 2 provides range and azimuthinformation continuously in response to continuous ground speed andheading information.

A source I of substantially constant voltage is connected to a pair ofadjustable voltage dividers 3 and 5, as shown in Figure 2. The movablearms of the voltage dividers 3 and 5 are ganged together, as indicatedby the dash line 1, for adjustment by means of a manually operable knob3. A pointer ll cooperates with a scale l3 to indicate the adjustment ofthe voltage dividers in terms of units of ground speed, such as milesper hour. The movable arms of the voltage dividers 3 and E 5 areconnected to respective terminals of a component solver device 15. Thedevice l5 includes a" sine card potentiometer, comprising a fiatresistor element l1 and a pair of slidable contacts l9 and 2! inengagement therewith. The terminals of the resistor element I 1 arethose which are connected to the voltage dividers 3 and 5.

measure, such as degrees.

cuit of .a motor control amplifier 33, which, in

turn, is connected to a reversible motor 35. The amplifier 33 and themotor 35 are arranged so that the motor 35 will run in a direction whichdepends on the polarity of the input to the art; forv example, theamplifier 33 may be a D.-C. amplifier, and the motor 35 may be a typedevice. Various known expedients may be employed to insure that thespeed of the motor shall be strictly proportional to the input voltage.Thus, the motor 35 may be provided with trol the energization of themotor. Since the foregoing is not essential to a clear understanding ofthe present invention, it need not be described in further detail.

The contact 2| of the component resolver device [5 is connected to anetwork including a variable resistor 31 and a fixed resistor 39. Themovable armof' the resistor 31- is coupled to a shaft 68. The resistor39 is connected to the input terminals of a motor control amplifier 43,which is similar to the amplifier 33 and is similarly connected to areversible motorAE.

The output shaft 41 of the motor 45 is coupled through differentialgearing -49xto an. indicator- 5!, which is calibrated in angularv terms,such as degrees. The differential .49 is arranged to enable theindicator shaft 53 to be adjusted-With respect to the motor shaft bymeans of a hand wheel 55. The indicator shaft 53 is coupled, asindicated by the dash line 51 to a pinion 59 which enga es the gearwheel- 3 ,I. A suitable gear ratio is'provided in thecouplirig'betweenthe shaft 53 and the pinion 59 to make the angularrotationS-of the gear 3 I and the shaft 53 equal.

k 'TI-'he shaft M of the motor 35 is coupled throughdiiferenti'algearing 6| to an indicator 53 calibrated in units of distance, such asmiles. The differential BI is arranged like the differential 49:.toallow the'iildicator shaft 65 to be displaced with respect to the motorshaft. 41- by rotations 'of a hand wheel 6I.-

' :l'nathe operation of theaboumdescribed system, it. is arbitrarilyassumed that a certain: number of" vo ts represents a ground speed. ofacertain arm is at a potential. positive with respect to ground and theother movable arm is at an equal potential negative with respect toground. Thus,

the voltage across the: resistance element .IT! is.

symmetrical with respect to ground and has a magnitude. depending.-uponthe adjustment of the knob 19. r

{the potential with respect to ground. at the contact IB- isproportional. to thecoSinebf the angle 18" between said contact and thelongitudi nal' axis (represented by the arrow 59) of the card: l1. Withthe parts in the position shown in :Figure 2, said angle 8 issubstantially 90 degre 1es-,.and the potential at-thecontact I9 is sub-1 stantially zero. If either part oi -the component solver I5 is rotatedwith respect to the-other, the

potential with the contact 19 willvary according tothe cosine of theangle of rotation.

$imilarly,- the potential: at the. Contact 2| is.

proportional to the sine of theangle 9. .As'sum ing-that the shaft 25 isrotatedclockwise from its fiducial' position through theangle a (seeFigure 1), and the gear 3'! is rotated counterclockwise from itsfiducial position throughthe angle a,

the angle ,8 will be 11-9.

Thus, the voltage appliedto the motor control. amplifier 33 willbe-proportional to;

T c; cos (m -Q5 corresponding to the rate of change of the ran e. Thus,vwhen the range R. is increasing, the output of the generator "I? will beof one polarity arbi-T. trarily designated as positive, and when therange This the radial component of the ground speed Since the motor'35runs. at a spe d which is put portional to the ratepfchangeof therahgeR,

the-total rotationot its; shaft is proportional 4- to the total changein R, and the indication displayed on the indicator 63 changesaccordingly. In order for the indicator 63 to show the true distance ofthe aircraft from the reference point, it must be initially adjusted bymeans of the hand wheel 6'! to show R0, the value of R at the pointwhere the craft is located when the operation of the equipment isstarted.

The potential at the contact 2| of the device [5 is proportional to:

VG Sin (a-0) VG sin (a 0) This quantity is the rate of change of. the.azir muth angle 0,.

The motor 45 rotates at a speed corresponding to said rate and,consequently, turns the shaft 41 through a total angle equivalent to thetotal. change in 0. The azimuth 60, corresponding to the position of theaircraft when the operation. of the system is started, is introduced bymeansof the hand wheel 55 so that the indicator it: will subsequentlyindicate the true valueof. than referred to'the line N-S inFigure 2.

Since the gear 3| is driven from the'shaft53" as described above, theangle (ct-*0) will be main-H tained between the parts of the resolverl5, r'e-' gardless of the variation of v.

Any changes in ground speed or heading during operation of the systemmay be inserted by corresponding adjustment oi the knobs .9' and 21:;The equipment will function continuously to in-i dicate at all times theposition of the aircraft in terms of and 19 referred to the point It beapparentwithout illustration that the shafts? B5 and 53 maybe used todrive other indicating; mechanism, for example, a crab, such asisiusedswith pilot training devices to plot a graph of'thef simulatedcourse followed.

A so, it within the contemplation of the.pres-.- ent invention that. theground speed and head-'1 ing information may be applied to' the systembyrotation of the shafts 1 and 25 automaticallyby measuring instrumentsor. the like, rather than:-

manually,

The system of Figure 3 produces the-opera-.=. tional steps of the systemof Figure 2 substan tially in reverse, providing ground speed andheading information continuously in response to; i continuousrangeand-azimuth information. I purpose of explanation, it is assumed thatthe azimuth and range information are available in terms of shaftrotations as by means of manually operable knobs -'H and 73,respectively.

The knob 1! drives a shaft 15' couped to arate generator 11 whichprovides an electrical output applied to a voltage divider 83 whosemovable contact is coupled to the range shaft 15, as indicated by thedash line 85.

.LThemovable contact of the voltage divided 83' is. coupled to amodulator 81. The rate genera tor 'l'lis coupled directly to .a' similarmodulator 89. Both'modulators 8'! and '89 are excited by m'ea'ns of anoscillator SH which'may operate at any suitable frequency, for example,400' cycles hour); The rotor winding 99 is connected to a motor controlcircuit I65. -The' motor control circuit I05 may be aibalanceddemodulator which provides an output having a-magnitude proportional tothe input thereto from the Winding ,fifl and a polarity which dependsupon the phase relationship betw'eenthis input and a referenc phaseinput. The second input to the motor control circuit I05 is supplied bythe oscillator ill. The output of the circuit IE5 energizes a reversiblemotor The output shaft I99 of the motor l! iscou pled to the rotor ofthe component resolver 93. The shaft I 99 is also coupled to one side ofa differential gear mechanism I II. The other side of the gear MI iscoupled to the azimuth shaft I09, as indicated b the dash line H3. Thespider of the diiferential l H is coupled to an indicator H calibratedin terms of azimuth (degrees) In the operation of the system of Figure3, the rate generator ll provides an output voltage proportional to therate of change of range,

at dt This quantity is the radial component VG cas (a- 8) of the groundspeed VG.

The rate generator 8| provides an output voltage proportional to therate of change of azimuth,

The voltage divider 83 is controlled by the range shaft 85 to modify theoutput of the generator 8! as a function of range so that the potentialwhich appears at the movable v vcontact of the voltage divider 83 isproportionalto the product of the range and the azimuth rate,

d 0 dt This quantity is the tangential component VG Sill (a0) of theground speed VG.

The rotor winding spect to the its reference position.

6, f The modulators 89 and Marc controlled by the respectiverate-proportional inputs and by the 400-cycle oscillator 9| to provide400-cycle out-1 put voltages whose amplitudes are proportionalrespectivel'y jto VG cos (a-0) and to VG sin (d-0) These outputs,applied to the orthogonally related windings 91 and 95 of'the componentresolver 83 produce therein a resultant magnetic field. 4 The amplitudeof the field in the resolver 93 is the vector sum of the componentfields produced by the windings 9'! and S5; and is proportional to Thedirection of the resultant field, referredto; the axis of the winding91, is:

The voltage induced by said field in the rotorwinding 99 depends uponthe angular position of said winding. As long as there is any suchvolt-- age, the motor control circuit is actuated'to; energize the motorIn! to drive the rotor toward a position such that the winding as isperpen dicular to the resultant field of the stator windings. When therotor is in this position, no voltage is induced in the winding 99 andthe motor stops. A maximum voltage, proportional to the amplitude of theresultant stator field and thus; proportional to VG, is induced in thewinding IE! I This yoltage is indicated, terms of ground; speed, by: themeter Hi3. '-With the rotor positioned as described, themotor shaft 1%isatangle (a6) with re-,

The differential gear I I! is rotated through this angle on one side bythe shaft ltd. The other side of. thedifierential is rotated through theangle 0 bythe shaft H3. The output shaft of the differential rotatesthrough the sum of these angles, which is the angle a and operates theindicator H5 to indicate heading.

As mentioned in connection with the description of Figure 2, the inputinformation may be supplied continuously, either manually or byautomatic means rotating the range and azimuth shafts, and the currentheading and ground speed information may be simply indicated asdescribed or may be used to actuate other equipment.

The described invention affords accurate and relatively simpleelectrical systems for converting between one type of flightinformation, such as that provided by radar, to another type ofinformation, such as that provided by airborne navigational instruments.

I claim as my invention:

1. In a flight simulator or the like, range and azimuth shafts to bedriven in accordance with respective positional coordinates, withrespect to a reference point, of an aircraft, electro-mechanicaltransducers coupled to said range and azimuth shafts respectively, acomponent solver device including two relatively movable parts, thefirst of said parts including one set of terminals connected to saidrange. shaft transducer and a second set of terminals connected to saidazimuth shaft transducer, said last-mentioned connection includingvariable voltage divider means coupled to said range shaft; means forrotating said parts of said component resolver with respect to eachother in accordance with the heading of said aircraft with respect to aradial line from said reference point to said craft; a heading shaft tobe driven in accordance with the heading of said craft with respect to.a fixed reference line such-as a; meridian through. said referencepoint, and means mechanically coupling said heading shaft to the secondof said parts of said component resolver: device, said last-mentionedpart includ ingat' least one set of terminals, and means deter-' miningthe voltage across said terminals in terms of the ground speed of saidaircraft; 7

-'-2; In a flight simulator or the .like'htwo'shafts, electro-mechanicaltransducers coupled to said first and second shafts respectively, acomponent solver device including two relatively movable parts, thefirst of said parts including one set of terminals connected to saidfirst transducer and a second set of terminals connected to said secondtransducer, variable .voltage divider means coupled to said first shaftand electrically coupled to said last-mentioned connection; means forrotating said parts of said componentre'solver with respect to eachother; a heading shaft and means mechanically coupling said headingshaft to the second of said parts of said component resol ver'de'vice',said last-mentioned part including at least one set of terminals, andmeans determining the voltage across said terminals.

3. Ina flight simulator or the like, range and azimuth shafts to bedriven in accordance with respective positional coordinates, withrespect to a reference point, of an aircraft, rate generators coupled tosaid range and azimuth. shafts respec:

m the otherin accordance with the. ratio r a e;

volages applied to said terminals from said ratcgenerators; a headingshaft and means including differential gearing mechanically couplingsaid heading shaft to the second of said parts of said componentresolver device, and to said azimuth shaft, said last-mentioned partincluding at least one set of terminals, and means indicating thevoltage across said-terminals.

4. In a flight simulator or the like, range and azimuth shafts, rategenerators coupled to said range and azimuth shafts respectively, acome. ponent solver device includingv two relatively mow able parts; thefirst of said parts including one set of terminals connected to saidrange. rate genera'tor and a'second set of terminals connectedto saidazimuth rate generaor, said last-mentioned; connection includingvariable voltage divider:

means coupled. to said range shaft; means for:

REFERENCES CITED The following references are of record in the file ofthis patent: UNITED STATES PATENTS Number Name Date 2,465,624 Agins Mar.29, 1949 2,467,646

Agins ..s Apr. 17,1949

